What is an ISWC?

An ISWC (International Standard Musical Work Code) is a permanent, internationally recognised reference number for a musical work: the song as a composition, regardless of who recorded it or who owns it (CISAC).

What it looks like

An ISWC is the letter T, then a nine-digit work number, then one check digit. Written out, the letters "ISWC" go in front, and hyphens or dots may be added for readability, for example ISWC T-345246800-1 (CISAC).

What it identifies, and what it does not

The ISWC identifies the work, not its manifestations. It does not identify recordings, sheet music or performances, and it does not record who owns what share or when the work was written (CISAC). Recordings have their own code, the ISRC.

Arrangements, lyric adaptations and translations each get their own ISWC, linked back to the original in the metadata. Lyrics on their own cannot get one, and a work does not need to be under copyright to be numbered (CISAC).

Who issues it

Creators and publishers cannot allocate their own ISWCs. Only authorised Registration Agencies assign them, and CISAC administers the system as the Registration Authority appointed by ISO (CISAC). For new works no extra step is needed: a number is assigned automatically as part of registering the work, and only once every creator on the work has been uniquely identified (CISAC). The minimum metadata is the title and all composers, authors and arrangers with their IPI numbers and roles (CISAC).

In practice that usually means registering the song with your performing rights organisation or publisher; see performing rights organisations explained and ISRC, ISWC and split sheets.

The code stays with the work for good: if a creator moves from one society to another, nothing happens to the ISWC (CISAC).

What we think

The rule that an ISWC is only issued once every writer is identified is the useful part for independent artists. A missing ISWC is usually a symptom, not the problem: it tends to mean a co-writer was never registered or the splits were never agreed. Settle the split sheet before release and the ISWC tends to follow; skip it and the song can sit unnumbered, which makes it harder to match to the right writers when it is used.